Certain electrochromic materials may change color when applying a voltage. The color change may be in the visible spectrum, but can also be, for example, in the near infrared (NIR), infrared (IR), or microwave spectral region. The change in color of an electrochromic material is usually due to reduction/oxidation (“redox”) processes within the electrochromic materials. Further, electrochromic devices may be switched between a substantially transmissive state and a substantially non-transmissive state depending upon the applied voltage. Indeed, electrochromic devices may be in a transmissive mode, in which light passes through the device and also modified by the device, and/or a reflective mode, in which light is reflected off the device and also modified by the device. Electrochromic devices composed of such materials may be developed wherein their transmissive properties may be adjusted or controlled.
To control electrochromic devices (in any region—Visible, IR or other), a small DC voltage may be applied. Such devices may utilize conducting polymers (CPs), inorganic metal oxides (MOs), or liquid crystals (LCs), for example. The DC voltage applied is generally <(+/−) 50 V in the case of LCs, <(+/−) 5 V in the case of MOs, and <(+/−) 3 V in the case of CPs.
In certain electrochromic devices, the voltage applied to the electrochromic device should generally not exceed certain maximum voltages. When the maximum applied voltage is exceeded (in which case an “overvoltage” or “overpotential” is said to be applied), irreversible oxidative or reductive degradation may occur, with consequent damage and cessation of function of the device. In the case of CP and MO devices, the redox stability limits for applied voltage are generally determined from the cyclic voltammogram (CV) of the system.
In evaluating the operability of such electrochromic devices, switching times are related to the applied voltage where increased voltage may, for example, cause the device to switch fast. However, the trade off is degradation of the device. Therefore, there exists a need in the field for devices and methods that allow for improved electrochromic switching, especially in devices comprising CPs, that do not degrade or destroy the electrochromic device